The present invention relates to a head construction which allows an oversized golf club head having a hollow portion and mainly made from a metal to be implemented.
What is most required of a golf club in the performance is longer distance and stabler directivity. Those called professionals can always hit a ball at the same one point of the face of a golf club, the distance is longer a because of their high swing speeds and the hit ball is well controlled in he directivity. Amateur golfers however cannot hit at a steady point of the face portion, therefore the distance is not long and the directivity is not stable.
The simplest way of overcoming the disadvantage is to increase the volume of a golf club head as much as possible. Thus increasing the volume of a head however increases the weight of the head and the golf club as a whole can be unbalanced in the case of some metal wood golf club heads which are recently mainstream products.
Therefore, in general, the thickness of the outer body material of a head is reduced, or the weight of material per unit area is reduced, in order to increase the size of the head.
Some models employ high strength material for further reducing the thickness of the head.
Japanese Patent Laying-Open No. 9-38248 discloses a golf club head having a dimple shaped recess at a face member in order to increase the strength as compared to a simple plate material, while Japanese Patent Laying-Open No. 4-135576 discloses a golf club head whose material has its crystal grain size adjusted in order to improve the toughness of the material.
Such golf club heads manufactured by the above conventional improvement methods however encounter with the following problems.
Regarding the method of thinning the outer body material of a head for increasing the size of the head, if the thickness of the outer body material of a head is reduced only in view of impact at the time of hitting a ball, such heads collide against each other in a caddie bag during transport, they could be easily dented by the weight applied on the thinned portion thereof. It is also highly possible that the heads are dented even with other minor impacts.
The use of high strength material for the outer body material of the head is disadvantageous because the high strength material itself is generally costly and materials which can be used are limited as a result.
The method disclosed by Japanese Patent Laying-Open No. 9-38248 to provide a dimple has not yet been clearly explained about the mechanism of strength improvement, and therefore it is not clear if the effect can be stably provided. Furthermore, the peripheral portion of the dimple could be thicker than the case of using a simple plate material, which disadvantageously increases the weight.
The method of reducing the crystal grain size as disclosed by Japanese Patent Laying-Open No. 4-135576 may be effective to cope with repetitive weight applied in hitting because the toughness of the material is improved, but the strength is not improved, and therefore the durability does not improve relative to the weight.
In view of the foregoing, it is a main object of the present invention to provide a golf club head having an outer body construction which allows the thickness to be reduced without loss in the strength in a golf club head having a hollow portion.
The present invention allows a thin and oversized golf club head having a hollow portion to be provided by providing the golf club head with a PCCP (pseudo-cylindrical concave polyhedral) structure so that the strength is increased.
According to an embodiment of the present invention, a golf club having a hollow portion can be entirely or partly provided with a PCCP structure excluding the face portion.
The present invention includes an application of the PCCP structure to a wood golf club head having a hollow portion.
In a wood golf club head having a hollow portion according to such an embodiment in which the PCCP structure is applied to the wood golf club head, the PCCP structure can be continuously provided to surround the head in a direction parallel to the face portion from the crown portion to the sole portion via both side portions excluding the back portion.
In a wood golf club head having a hollow portion, the PCCP structure can be continuously provided in a direction perpendicular to the face portion from the crown portion via the back portion to the sole portion.
Furthermore, in a wood golf club head having a hollow portion, the crown portion and sole portion can be entirely or partly provided with the PCCP structure, or only the crown portion can be provided with the PCCP structure.
As a PCCP structure applied according to the present invention, for example, such a structure is employed in which the bases of each pair of triangles arranged adjoined with each other in a diamond shape define a thalweg, and the inclined sides define ridgelines to define a cylindrical shape. Such a PCCP structure may be employed in which the bases of each pair of trapezoids arranged adjoined with each other to form a hexagon define a thalweg, and the upper sides and the nonparallel sides define ridgelines so as to define a cylindrical shape. The vertexes of the thalweg and ridgelines are formed for example to define an obtuse angle or circular segment.